The present invention is directed to bicycle brake devices and, more particularly, to bicycle brake devices that are used to brake a hub of a bicycle wheel.
Bicycle braking devices currently available include rim braking devices and hub braking devices. Rim braking devices include cantilever brakes or caliper brakes that brake the rim of the wheel. Hub braking devices brake the wheel hub, and they include drum brakes, band brakes, roller brakes and the like.
A hub brake brakes the hub of the wheel, so it is able to provide braking even if the wheel rim is warped. Drum brakes and roller brakes, which are hub braking devices of this kind, effect braking by means of friction created when the inside peripheral face of a tubular brake drum that rotates in unison with the wheel hub is contacted by a brake shoe. In a roller brake, rollers spaced apart in the circumferential direction are displaced diametrically outwardly by a cam to move the brake shoe. Grease usually is injected into the interior of a roller brake to ensure smooth displacement of the rollers.
In some brake devices of this kind, a brake drum may be formed from a stainless steel alloy with a brake face on its inner peripheral surface. The brake drum may be provided with a cooling disk having fins that may be fabricated of aluminum alloy. Such a cooling disk has a high heat transfer capability to dissipate the heat generated by contact between the brake shoe and the brake face of the brake drum. As a result, thermally induced deterioration in braking performance can be held in check.
One possible approach to fastening the cooling disk to the brake drum involves inserting the brake drum in a mold and insert molding to form the cooling disk. However, when the cooling disk is fastened to the brake drum by an integral molding process, there is a risk of problems such as discoloration or deformation of the brake drum due to the heat of molding, since the brake drum is fabricated of metal. Parts that have been subjected to metal plating are particularly susceptible to discoloration during insert molding. Discoloration and deformation require manual touchup in a subsequent process, thus resulting in a more complicated production process and higher production costs. Integral molding also requires the transportation of the brake drums to separate locations where casting equipment is located. The brake drums then must be properly positioned in the mold. This creates a laborious and complicated production process as well as the need for complicated and expensive forming molds, thus further increasing production costs.